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Climbing obesity rates around the world aren't a concern; they've now become a full-fledged problem.

Source: Centers for Disease Control & Prevention.

In the "Global Burden of Disease" report from the World Health Organization, which was compiled over a 20-year period from 1990 through 2010 using data from 500 researchers from 50 countries, it was determined that obesity had surpassed hunger as the greatest worldwide threat. With the exception of sub-Saharan Africa, obesity rates shot up globally by 82%. In the U.S., the obesity rate is a staggering 35.7%.

Obesity isn't just an individual killer, either; it affects those around us -- our family and friends -- both directly and indirectly. Obesity and the health problems that often accompany it are linked to $190 billion in annual health costs, or approximately 21% of all health expenditures. What's more, obesity costs U.S. businesses $164 billion annually because of health problems associated with being overweight, according to the Society of Actuaries. You can read about more flabbergasting costs associated with obesity from my Foolish colleague Keith Speights.

The point of the matter is that changes need to be undertaken now to halt this rising obesity trend in its tracks; otherwise we could be looking at an overwhelmed global health system as early as a decade from now. If we do nothing, then the following top five diseases caused by obesity are almost certain to climb. While disappointing from a human perspective, it's a boon for pharmaceutical companies that'll reap the benefits of the world's widening waistline.

Fifth most common disease caused by obesity: Cancer I recently finished examining the 12 most commonly diagnosed types of cancer and was pretty shocked to discover that obesity was a risk factor for quite a few. An inactive lifestyle puts people at a higher risk of developing breast, colorectal, endometrial, and kidney cancers, just to name a few. What's most concerning about the aforementioned cancer types are that some are among the deadliest with regard to five-year survival rates (depending on stage).

If obesity rates don't decline, a biopharmaceutical company like Onyx Pharmaceuticals , which has an oral medication known as Stivarga to treat advanced colorectal cancer, will clearly benefit. Onyx projects that Stivarga, which works by inhibiting membrane-bound and intracellular kinases, could have peak sales in excess of $1 billion. Onyx receives a 20% royalty interest on net sales of the drug, with the remainder going to partner Bayer.

Fourth most common disease caused by obesity: Stroke This one should be fresh in everyone's mind, as we covered the top three risk factors for stroke last weekend. Not surprisingly, being overweight or obese was a risk factor for a laundry list of the medical conditions that can exacerbate a person's chance of having a stroke, including hypertension, high cholesterol, heart disease, and type 2 diabetes. Nearly 800,000 people had a stroke in 2010, with 130,000 of them dying. If obesity trends rise, the propensity of stroke occurrences is also likely to rise.

If that's the case, then it could mean big business for the duo of Arena Pharmaceuticals and VIVUS , which both have chronic weight-management drugs approved by the Food and Drug Administration. Arena's Belviq was approved in June last year but only made it to pharmacy shelves within the past week, as it had been awaiting scheduling from the Drug Enforcement Agency. VIVUS' Qsymia, on the other hand, has been available to the public since November, although sales have been tempered because few insurance companies are covering the drug thus far. It should be interesting to see which drug comes out on top, as Belviq had a better safety profile in clinical trials, but Qsymia offered the better overall weight-loss results in trials in percentage terms. Perhaps the pie is big enough for both companies to succeed?

Third most common disease caused by obesity: Nonalcoholic fatty liver disease If there is some twisted bright spot on this list of top diseases caused by obesity, it's that the third most common disease, fatty liver disease, isn't deadly in its most common form. In fact, quite a bit of the population is likely to have fatty liver disease, which will go undetected, because in its early and mid-level stages it doesn't present any symptoms. Outside of scarring of the liver, a person wouldn't even notice. The danger is if this nonalcoholic fatty liver disease progresses into what's known as nonalcoholic steatohepatitis, or silent liver disease, which can lead to cirrhosis (i.e., permanent scarring), and eventually complete failure, of the liver.

The downside to silent liver disease is that there is no current standard of treatment -- at least as it pertains to drugs. The most logical way to treat the disease is by inducing weight loss as quickly as possible, but even that offers no guarantee of success.

Second most common disease caused by obesity: Cardiovascular diseases This broad-based topic can cover a myriad of problems ranging from hypertension and high cholesterol to full-blown heart arrhythmia or heart disease. While the latter two are more dangerous on an immediate basis than the former two, heart disease is the leading cause of death in the United States. Being overweight puts excess pressure on all of the body's organs to function properly, greatly increasing the probability of a complication or series of complications.

If obesity trends move higher globally, long-term LDL-cholesterol-lowering drugs (the bad type of cholesterol) are going to make a fortune. Liptruzet, for example, won FDA approval last month and is a combination of a statin -- in this case, Pfizer's now generic Lipitor -- and Merck's cholesterol absorption inhibitor, Zetia. Separately, Lipitor and Zetia reduced LDL-cholesterol by 37% to 54%, and 20% in trials. When combined as Liptruzet, this LDL reduction jumped to 53% to 61%, depending on the dosage. This next-generation LDL-cholesterol-fighting drug could be the next big thing in long-term high-cholesterol maintenance.

An astonishing 25.3 million people in the U.S. already have some form of diabetes, be it type 1, which is inherited at birth, or type 2, whose onset is based on diet, exercise, and other factors. An additional 79 million people are pre-diabetic, meaning the likelihood of seeing more diabetes diagnoses over the coming decade is very high. Diabetes offers a myriad of complications including kidney failure and is the leading cause of new diagnoses of blindness and non-accident-related amputations of the feet and legs.

If there is some semblance of a bright spot here, it's that the FDA recently approved a new class of diabetes drug by Johnson & Johnson known as Invokana. Rather than working from the pancreas or liver as previous diabetes medications had, Invokana is an SGLT-2 inhibitor that works in the kidneys and allows a person to excrete excess glucose through the urine. The drug not only provides improved glycemic balance, but it's also been shown to induce weight loss and lower blood pressure -- two fantastic benefits for patients who are overweight or obese.

The takeawayThere are no two ways about it: Obesity is a growing global dilemma. Clearly, the best way to deal with rising levels of obesity is to educate people about the need for proper diet and exercise. Understandably, this won't work completely for everyone, as genetic make-up, age, and severity of the disease will play a big role in total weight loss, but a little exercise certainly never hurt anyone.

In cases where exercise isn't enough, pharmaceutical companies look poised to step in and lend a helping hand. Bad cholesterol-blocking drugs like Liptruzet and J&J's Invokana, which aids in glycemic balance, will certainly keep some of obesity's most dangerous health symptoms at bay. Arena and VIVUS' weight control management drugs, though, have the potential to truly change the course of obesity treatment if they can gain the acceptance of physicians and health-benefit providers.

Who will win the obesity-drug market?Can VIVUS pick up its lagging sales and fend off the competition, or will Arena Pharmaceuticals reign supreme in the obesity space? If you're in the dark, grab copies of The Motley Fool's premium research reports on VIVUS and Arena Pharmaceuticals to stay up to date. Senior biotech analyst Brian Orelli gives investors the must-know information, including an in-depth look at the obesity market and reasons to buy and sell both stocks. Click now for an exclusive look at Arena and VIVUS -- complete with a full year of free updates -- today.